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1.
The experimental studies have provided evidence of the occurrence of transitions from the 3T1g(3F) ground state to the crystal-field levels 3T2g(3F), 3T1g(3P) and 3A2g(3F) for the V3+ centres in Al2O3 crystal; and from the 3A2g(3F) ground state to the crystal-field levels 3T2g(3F), 3T1g(3F) and 3T1g(3P) for the Ni2+ centres in LiNbO3 crystal (levels are assigned to irreps of the Oh point symmetry group). Using the experimental spectroscopic data, theoretical calculations of the crystal-field levels of V3+:Al2O3 and Ni2+:LiNbO3 are carried out based on the Racah theory. The observed crystalline-field splittings of the V3+ and Ni2+ terms were accounted for using a C3 symmetry Hamiltonian. The spin-orbit interaction was taken into account in this work. The Racah, crystal-field and spin-orbit parameters, which fit experimental and theoretical energy levels, have been reliably obtained. A good agreement between the theoretical and experimental results for the energy levels of V3+:Al2O3 and Ni2+:LiNbO3 has been obtained.  相似文献   

2.
The single crystal of [Ni(ina)2(H2O)4]·(sac)2, (NINS), (ina is isonicotinamide and sac is saccharinate) complex has been prepared and its structural, spectroscopic and thermal properties have been determined. The title complex crystallizes in monoclinic system with space group P21/c, Z=2. The octahedral Ni(II) ion, which rides on a crystallographic centre of symmetry, is coordinated by two monodentate ina ligands through the ring nitrogen and four aqua ligands to form discrete [Ni(ina)2(H2O)4] unit, which captures two saccharinate ions in up and down positions, each through intermolecular hydrogen bands. The magnetic environment of copper(II) doped NINS crystal has also been identified by electron paramagnetic resonance (EPR) technique. The g and A values of Cu2+ doped NINS single crystal were calculated from the EPR spectra recorded in three mutually perpendicular planes. These values indicated that the paramagnetic centre has a rhombic symmetry with the Cu2+ ion having distorted octahedral environment. The complex exhibits only metal centred electroactivity in the potential range of −2.00, 1.25 V versus Ag/AgCl reference electrode.  相似文献   

3.
Optical absorption spectra of Ni2+ in (NH4)2Mg(SO4)2·6H2O and Co2+ in Na2Zn(SO4)2·4H2O single crystals have been studied at room and liquid nitrogen temperatures. From the nature and position of the observed bands, a successful interpretation could be made assuming octahedral symmetry for both the ions in the crystals. The splitting observed for 3T1g(F) band in Ni2+ and 4T2g(F) band in Co2+ at liquid nitrogen temperature have been explained as due to spin-orbit interaction. The extra band observed at 16,325 cm-1 in the case of Ni2+ at low temperature has been interpreted to be the superposition of vibrational mode of SO2-4 radical on 3T1g(F) band. The observed band positions in both the crystals have been fitted with four parameters B, C, Dq and ζ.  相似文献   

4.
Using the 2,5-bis(2-pyridyl)-1,3,4-thiadiazole (bptd), we recently prepared [Cu2(bptd) (H2O) Cl4] and [Ni2(bptd)2 (H2O)4] Cl4, 3H2O in which the magnetic centres are connected through one diazine+one chloro and two diazine ligand bridges, respectively. These two compounds are the first examples that show null intramolecular magnetic interactions despite M-M distances close to 3.7 Å within perfectly planar edifices:Down to , [Cu2(bptd)Cl4(H2O)] is paramagnetic while, below Tt, half of the Cu2+ions interact, leading to residual paramagnetism of one Cu2+/f.u. Magnetic susceptibility measurements, EPR and pulsed EPR study indicate the original intermolecular nature of AF exchanges.[Ni2(bptd)2(H2O)4]Cl4·3H2O susceptibility obeys a Curie-law involving pure paramagnetism. Moreover, its EPR spectrum can be interpreted on the basis of virtual S=1 monomers. Below 70 K, Zero Field Splitting (D∼275 G) due to dipolar interactions without magnetic exchanges could be responsible for the LT spectra splitting. For both compounds, the thia role is suggested as partially responsible for the null-in-plane magnetic exchanges.  相似文献   

5.
The low-temperature single-crystal polarized absorption and the luminescence spectra of Cs2[CrCl2(H2O)4]Cl3 are theoretically analyzed in order to determine the electronic structure of the trans-[CrCl2(H2O)4]+ complex. This study, based on the Racah theory, leads to a good agreement between the theoretical and experimental energy levels. The electronic-exited state 4T2g(Oh) is split into 4Eg and 4B2g components due to the lowering of the symmetry from Oh to D4h. The polarized absorption spectrum and the theoretical energies show that the 4Eg(D4h) state is lower in energy than the 4B2g(D4h) state. The resolved vibronic structure in the luminescence spectrum reveals a progression in a non-totally symmetric b1g mode, a manifestation of a Jahn-Teller effect in the emitting state 4T2g(Oh). Both Jahn-Teller and spin-orbit coupling in the orbitally degenerated 4Eg(D4h) state are necessary to account for the spectroscopic observations.  相似文献   

6.
A new compound, K4(SO4)(HSO4)2(H3AsO4) was synthesized from water solution of KHSO4/K3H(SO4)2/H3AsO4. This compound crystallizes in the triclinic system with space group P1¯ and cell parameters: a=8.9076(2) Å, b=10.1258(2) Å, c=10.6785(3) Å; α=72.5250(14)°, β=66.3990(13)°, γ=65.5159(13)°, V=792.74(3) Å3, Z=2 and ρcal=2.466 g cm−3. The refinement of 3760 observed reflections (I>2σ(I)) leads to R1=0.0394 and wR2=0.0755. The structure is characterized by SO42−, HSO4 and H3AsO4 tetrahedra connected by hydrogen bridge to form two types of dimer (H(16)S(3)O4?S(1)O42− and H(12)S(2)O4?H3AsO4). These dimers are interconnected along the [1¯ 1 0] direction by the hydrogen bonds O(3)-H(3)?O(6). They are also linked by the hydrogen bridge assured by the hydrogen atoms H(2), H(3) and H(4) of the H3AsO4 group to build the chain S(1)O4?H3AsO4 which are parallel to the “a” direction. The potassium cations are coordinated by eight oxygen atoms with K-O distance ranging from 2.678(2) to 3.354(2) Å.Crystals of K4(SO4)(HSO4)2(H3AsO4) undergo one endothermic peak at 436 K. This transition detected by differential scanning calorimetry (DSC) is also analyzed by dielectric and conductivity measurements using the impedance spectroscopy techniques. The obtained results show that this transition is protonic by nature.  相似文献   

7.
用二次组态相关(QCISD)和密度泛函(B3LYP)方法, 选用6-311++g(d,p), 6-311++g(3df,3pd)和D95(3df,3pd)基组对H2, BeH和BeH2分子的结构进行优化. 得到它们的基态电子态分别为H2(1Σg), BeH(2Σ)和BeH2(1Σg 关键词: BeH 2')" href="#">BeH2 2')" href="#">H2 二次组态相关(QCISD) 势能函数  相似文献   

8.
We present aborption spectra of an oriented single crystal of MnK4H2(SO4)4, 2H2O at temperatures between 20 and 1.6 K. This salt has orthorhombic symmetry and gives, both in the visible and ultraviolet regions, an absorption spectrum which changes considerably when the temperature decreases from 20 to 4.2 K. The spectrum has sharp lines at 1.6 K in the two absorption regions corresponding to teh excited levels 4A14E(4G) and 4T2(4D). A study has been made of the Zeeman splitting of these sharp lines; a discontinuity has been observed in the Zeeman splitting as a function of magnetic field at 1.6 K. This discontinuity is a consequence of a magnetically-ordered phase.  相似文献   

9.
EPR spectra of Gd3+-doped Ce2(SO4)3.8H2O and La2(SO4)3.9H2O single crystals have been measured with an X-band spectrometer at room and low temperatures. The absolute signs of spin Hamiltonian parameters have been determined for the La2(SO4)3.9H2O host from intensities of lines at liquid helium temperature; for the Ce2(SO4).8H2O host the lines broaden considerably below 60 K, not permitting the determination of absolute signs of spin Hamiltonian parameters. The data are analysed using a rigourous least-squares procedure, fitting simultaneously all lines obtained for several orientations of the external magnetic field. The zero-field splittings have been computed for both the hosts. The characteristics of EPR spectra of Gd3+ in these hosts are compared with those obtained in other rare-earth trisulphate octahydrate hosts.  相似文献   

10.
Optical transitions in normal-spinel Co3O4 have been identified by investigating the variation of its optical absorption spectrum with the replacement of Co by Zn. Three optical-transition structures were located at about 1.65, 2.4, and 2.8 eV from the measured dielectric function of Co3O4 by spectroscopic ellipsometry. The variation of the absorption structures with the Zn substitution (ZnxCo3−xO4) can be explained in terms of charge-transfer transitions involving d states of Co ions. The 1.65 eV structure is assigned to a d-d charge-transfer transition between the t2g states of octahedral Co3+ ion and t2 states of tetrahedral Co2+ ion, t2g(Co3+)→t2(Co2+). The 2.4 and 2.8 eV structures are interpreted as due to charge-transfer transitions involving the p states of O2− ion: p(O2−)→t2(Co2+) for the 2.4 eV absorption and p(O2−)→eg(Co3+) for the 2.8 eV absorption. The observed gradual reduction of the 1.65 and 2.4 eV absorption strength with the increase of the Zn composition for ZnxCo3−xO4 can be explained in terms of the substitution of the tetrahedral Co2+ sites by Zn2+ ions. The crystal-field splitting ΔOh between the eg and the t2g states of the octahedral Co3+ ion is estimated to be 2 eV.  相似文献   

11.
Alkaline hexafluorostantanate red phosphors Na2SnF6:Mn4+ and Cs2SnF6:Mn4+ are synthesized by chemical reaction in HF/NaMnO4 (CsMnO4)/H2O2/H2O mixed solutions immersed with tin metal. X-ray diffraction patterns suggest that the synthesized phosphors have a tetragonal symmetry with the space group D4h14 (Na2SnF6:Mn4+) and a trigonal symmetry with the space group D3d3 (Cs2SnF6:Mn4+). Photoluminescence (PL) analysis, PL excitation (PLE) spectroscopy, and the Raman scattering techniques are used to investigate the optical properties of the phosphors. The Franck-Condon analysis of the PLE data yields the Mn4+-related optical transitions to occur at ∼2.39 and ∼2.38 eV (4A2g4T2g) and at ∼2.83 and ∼2.76 eV (4A2g4T1g) for Na2SnF6:Mn4+ and Cs2SnF6:Mn4+, respectively. The crystal field parameters (Dq) of the Mn4+ ions in the Na2SnF6 and Cs2SnF6 hosts are determined to be ∼1930 and ∼1920 cm−1, respectively. Temperature-dependent PL measurements are performed from 20 to 440 K in steps of 10 K, and the obtained results are interpreted by taking into account the Bose-Einstein occupation factor. Comprehensive discussion is given on the phosphorescent properties of a family of Mn4+-activated alkaline hexafluoride salts.  相似文献   

12.
EPR spectroscopic investigations on single crystals of diaquabis[malonato(1-)-κ2O,O′] zinc(II) doped with VO(II) ion have been carried out at X-band frequencies and at 300 K. The single crystal, rotated along the three mutually orthogonally axes, has yielded spin-Hamiltonian parameters g and A as: gxx=1.980, gyy=1.972, gzz=1.937 and Axx=8.4, Ayy=6.1, Azz=18.1 mT, respectively. These spin-Hamiltonian parameters reflect a slight deviation from axial symmetry to rhombic, which is elucidated by the interstitial occupation of vanadyl ions. The isofrequency plots and powder EPR spectrum have been simulated. The percentage of metal-oxygen bond has been estimated. The optical absorption spectrum exhibits four bands at 257, 592, 720 and 764 nm suggesting a C4v symmetry. The admixture coefficients and bonding parameters have also been calculated by collaborating EPR data with optical data.  相似文献   

13.
Recently, we have discovered a new type of first order phase transition around 120 K for (n-C3H7)4N[FeIIFeIII(dto)3] (dto=C2O2S2), where the charge transfer transition between FeII and FeIII occurs reversibly. In order to elucidate the origin of this peculiar first order phase transition. Detailed information about the crystal structure is indispensable. We have synthesized the single crystal of (n-C3H7)4N[CoIIFeIII(dto)3] whose crystal structure is isomorphous to that of (n-C3H7)4N[FeIIFeIII(dto)3], and determined its detailed crystal structure. Crystal data: space group P63, a=b=10.044(2) Å, c=15.960(6) Å, α=β=90°, γ=120°, Z=2 (C18H28NS6O6FeCo). In this complex, we found a ferromagnetic transition at Tc=3.5 K. Moreover, on the basis of the crystal data of (n-C3H7)4N[CoIIFeIII(dto)3], we determined the crystal structure of (n-C3H7)4N[FeIIFeIII(dto)3] by simulation of powder X-ray diffraction results.  相似文献   

14.
In this work, two d-d transition spectra and four EPR parameters g, g, A, A of K2PdCl4/Cu2+ are uniformly interpreted based on Zhao's crystal-field model. The calculation result is in good agreement with the experiment findings. The ligand spin-orbit coupling is neglected on the calculation, which is consistent with the ab initio result by Hillier et al. [J. Am. Chem. Soc. 98 (1976) 95]  相似文献   

15.
The chemical preparation, the calorimetric studies and the crystal structure are given for two new organic sulfates NH3(CH2)5NH3SO4 1.5H2O (DAP-S) and NH3(CH2)9NH3SO4·H2O (DAN-S). DAP-S is monoclinic P21/n with unit cell dimensions: a=11.9330(2) Å; b=10.9290(2) Å; c=17.5260(2) Å; β=101.873(1)°; V=2236.77(6) Å3; and Z=8. Its atomic arrangement is described as inorganic layers of units and water molecules separated by organic chains. DAN-S is monoclinic P21/c with unit cell parameters: a=5.768(2) Å; b=25.890(10) Å; c=11.177(5) Å; β=115.70(4)°; V=1504.0(11) Å3 and Z=4. Its structure exhibits infinite chains, parallel to the [100] direction where the organic cations are interconnected. In both structures a network of strong and weak hydrogen bonds connects the different components in the building of the crystal.  相似文献   

16.
The electron paramagnetic resonance (EPR) spectral data (the g factors and hyperfine structure constants) and d–d transition spectra for the tetragonal Mo5+ centre in [Mo6O19][N(C4H9)4]3 salt are theoretically investigated from the complete diagonalization method (CDM) for a 4d1 ion in tetragonally compressed octahedron. The theoretical results are in good agreement with the experimental data. The dependency of the g factors of the ground state on the R(MoO bond length) has been studied. It is shown that the g factors varied with the R approximately in a linear way.  相似文献   

17.
The g factor of Cr4+ in Y2SiO5 crystal is calculated from a completed high-order perturbation formula, in which not only the conventional contribution to the g-shift Δg(=gge) from the crystal-field mechanism, but also the contribution from the charge-transfer mechanism (which is neglected in the crystal-field theory) are considered. The calculated result shows good agreement with the observed value. It is found that the calculated Δg due to the charge-transfer mechanism is opposite in sign and about 38% in magnitude, compared with that due to the crystal-field mechanism. So, in the studies of the g factor for a 3dn ion having high valence state in crystals, the contribution due to the charge-transfer mechanism should be taken into account.  相似文献   

18.
With the help of group theory analysis of absorption spectra of the transition 3H63F3 of Tm3+ ion in TmAl3(BO3)4 crystal, measured at several temperatures from 1.8 till 293 K, it has been shown, that the local symmetry of the Tm3+ environment is C3 and it decreases to C1 at a low temperature. Effective selection rules and polarizations of lines at high enough temperatures (when the line-width is larger than the splitting in C3 symmetry) have been obtained.  相似文献   

19.
The excitation spectrum of the Mn2+ emission has been measured in CaF2 and CdF2. The observed excitation bands have been assigned to transitions of the Mn2+ ions in a cubic environment. The calculated values for the crystal field (Dq) and Racah parameters (B,C) are Dq = 425 cm-1 for CaF2, Dq = 500 cm-1 for CdF2 and, B = 770 cm-1 and C / B = 4.48 for both compounds. The lifetime of the fluorescent level 4T1g(4G) has been measured in both compounds at different temperatures in the range from 10 to 500 K. The lifetime thermal dependence is explained taking into account different mechanisms (purely radiative, phonon assisted, and radiationless transitions) for the decay of excited Mn2+ ions.  相似文献   

20.
By using diamond anvil cell (DAC), high-pressure Raman spectroscopic studies of orthophosphates Ba3(PO4)2 and Sr3(PO4)2 were carried out up to 30.7 and 30.1 GPa, respectively. No pressure-induced phase transition was found in the studies. A methanol:ethanol:water (16:3:1) mixture was used as pressure medium in DAC, which is expected to exhibit nearly hydrostatic behavior up to about 14.4 GPa at room temperature. The behaviors of the phosphate modes in Ba3(PO4)2 and Sr3(PO4)2 below 14.4 GPa were quantitatively analyzed. The Raman shift of all modes increased linearly and continuously with pressure in Ba3(PO4)2 and Sr3(PO4)2. The pressure coefficients of the phosphate modes in Ba3(PO4)2 range from 2.8179 to 3.4186 cm−1 GPa−1 for ν3, 2.9609 cm−1 GPa−1 for ν1, from 0.9855 to 1.8085 cm−1 GPa−1 for ν4, and 1.4330 cm−1 GPa−1 for ν2, and the pressure coefficients of the phosphate modes in Sr3(PO4)2 range from 3.4247 to 4.3765 cm−1 GPa−1 for ν3, 3.7808 cm−1 GPa−1 for ν1, from 1.1005 to 1.9244 cm−1 GPa−1 for ν4, and 1.5647 cm−1 GPa−1 for ν2.  相似文献   

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